Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Qual é a média de notas da escola de Fairfield?
 ###Tabelas: CREATE TABLE wrestling (wrestling_id AUTO_INCREMENT PRIMARY KEY, Athlete VARCHAR, Event VARCHAR, Round 1 VARCHAR, Round 2 VARCHAR, Round 3 VARCHAR, Round 4 VARCHAR, Round 5 VARCHAR, Final VARCHAR) CREATE TABLE comparison_of_toy_group_breeds_of_major_kennel_clubs (comparison_of_toy_group_breeds_of_major_kennel_clubs_id AUTO_INCREMENT PRIMARY KEY, The Kennel Club (UK) Toy Group VARCHAR, Canadian Kennel Club Toy Dogs Group VARCHAR, American Kennel Club Toy Group VARCHAR, Australian National Kennel Council Toy Dogs Group VARCHAR, New Zealand Kennel Club Toy Group VARCHAR) CREATE TABLE dunedin_city (dunedin_city_id AUTO_INCREMENT PRIMARY KEY, Name VARCHAR, Years VARCHAR, Gender VARCHAR, Area VARCHAR, Authority VARCHAR, Decile INT, Roll INT) CREATE TABLE investment (investment_id AUTO_INCREMENT PRIMARY KEY, 2005 INT, 2006 INT, 2007 INT, 2008 INT, 2009 INT, 2010 INT, Total INT, Average annual INT) CREATE TABLE owned-and-operated (owned-and-operated_id AUTO_INCREMENT PRIMARY KEY, City of license/market VARCHAR, Station VARCHAR, Channel TV ( RF ) VARCHAR, Year of affiliation INT, Year of disaffiliation INT)  
SELECT AVG Roll FROM dunedin_city WHERE Name = fairfield school